Question: On the first 4 exams of his chemistry class, Michael got an average score of 82. What does he need on the next exam to have an overall average of 85?
Explanation: Let his score on the next exam be $x$ The sum of all of his scores is then $4 \cdot 82 + x$ The same sum must also be equal to $5 \cdot 85$ Solve: $x = 5 \cdot 85 - 4 \cdot 82 = 97$.